Ch. 18 - Evolution of Populations

Question 1

gene pool

Answer 1

• all the genes, including all the different alleles for each gene, that are present in a population at any one time

Question 2

allele frequency

Answer 2

• the number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene

Question 3

single - gene trait

Answer 3

• trait control by one gene that has two alleles

Question 4

polygenic trait

Answer 4

• trait control by two or more genes

Question 5

directional selection

Answer 5

• form of natural selection when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

Question 6

stabilizing selection

Answer 6

• form of natural selection in which individuals near the center of a distribution curve have higher fitness than individuals at either end of the curve

Question 7

disruptive selection

Answer 7

• natural selection in which individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle of the curve

Question 8

genetic drift

Answer 8

• random change in allele frequency caused by a series of chance occurrences that cause an allele to become more or less common in a population

Question 9

bottleneck affect

Answer 9

• a change in allele frequency following a dramatic reduction in the size of a population

Question 10

genetic equilibrium

Answer 10

• situation in which allele frequencies in a population remain the same

Question 11

Hardy - Weinberg principle

Answer 11

• principal that states that allele frequencies in a population remain the same unless one or more factors caused those frequencies to change

Question 12

sexual selection

Answer 12

• when individuals select mates based on heritable traits

Question 13

gene flow

Answer 13

• the movement of genes into or out of a population

Question 14

speciation

Answer 14

• formation of a new species

Question 15

reproductive isolation

Answer 15

• separation of a species or population so that they no longer interbreed and evolve into separate species

Question 16

behavioral isolation

Answer 16

• form of reproductive isolation in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding

Question 17

geographical isolation

Answer 17

• form of reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains, or bodies of water, leading to the formation of two separate subspecies

Question 18

temporal isolation

Answer 18

• form of reproductive isolation in which two or more species reproduces at different times

Question 19

Hox gene

Answer 19

• a group of homeotic genes clustered together that determines the head to tail identity of body parts in animals. All Hox genes contain the homobox DNA sequence

Question 20

Founder effect

Answer 20

• a change in allele frequencies as a result of the migration of a small subgroup of a population; new population has less genetic diversity than original population